Conversion of hydrocarbon oils and gases



March 12, 194o.

GAS CHARGE OIL CHARGE R. L. SAVAGE, JR

FRACTIONATOR ATTORNEY Patented Man 12, 1940 CONVERSION OF HYDROC'ARBON OILS AND GASES Rufus L. Savage, Jr., Port Arthur, Tex., assignor, by mesne assignments, to Texaco Development Corporation, New York, N. Y., a, corporation of Delaware Application August 5, 1937, Serial No. 157,481

Claims. (Cl. 196-62) This invention relates to the manufacture of motor fuel by conversion of hydrocarbon oils and gases, outside the gasoline boiling point range,

into products within the gasoline boiling point range. with the conversion of higher boiling point oils into lower boiling point products in the presence of normally gaseous hydrocarbons and hydrogen, whereby combined cracking, polymerization and m hydrogenation, as well as reactions of the nature of gas reversion, and inhibition of polymerization of higher boiling unsaturated products into tarry materials susceptible to coke formation,

occur.

It has been proposed heretofore to crack hydrocarbon oils in the presence of added normally gaseous hydrocarbons to obtain gas .reversion or produce the simultaneous and joint cracking and polymerization of the oil and gases, as well as interaction between the oil and gas to obtain intermediate boiling point products` In cracking hydrocarbon oils into lower boiling point products, such as gasoline, higher boiling unsaturated products are formed which tend to polymerize to tar or pitch and which are believed to be often responsible for coke difficulties. It V has been found that by conducting the cracking operation in the presence of normally gaseous hydrocarbons, substantially less coke formation results,

dueto the inhibiting effect 'of normallyy gaseous hydrocarbons; or a combination of the gaseous hydrocarbons with the unsaturated higher boi'- ing point oils to form intermediate boiling point products, which areless susceptible to coke formation, takes place.

In accordance with the present invention. it

is intended to add the normally gaseous hydrocarbons and the hydrogen under condtions'which will give the maximum conversion into high quality motor fuel products and to produce minimum formation of coke. In order to do this it is preferable to subject the oil and the normally gaseous hydrocarbons to conversion conditions whereby the maximum benet from the gasesis obtained prior to the reaction in the presence of the hydrogen; however, it is to be understood that the oi,V

The invention has to do particularlyI bon oils to cracking or incipient cracking and,

prior to substantial polymerization to coke forming materials, to incorporate with the hot products the normally gaseous hydrocarbons and then subject the mixture to reaction whereby the maximum benefits of the gaseous-hydrocarbons are obtained. The hydrogen is then incorporated Withthe reaction products, whereby further con-A version may be obtained under conditions to obtain the maximum benefit of the hydrogen.

It will be observed that a Aprocess is provided whereby combination cracking and gas polymerlization, or gas reversion, is obtained, the gaseous obtain maximum benet, particularly with respect to inhibiting tar and' coke formation and hydrocarbons. Reactions in the nature of hydrogenation will also be effected which will fury ther prevent and retard undesirable polymerization reactions which result in the formation of fuel oils and often in the ultimate production of coke. l l

The process may be carried out with or without the aid of a hydrogenation catalyst, or one or more of the separate steps may be conducted in the presence of a hydrogenation catalyst. It is often desirable to at least carry out a portion of the reaction in the presence of a catalyst. A catalyst for this purpose may be any preferred or well known hydrogenation catalyst and preferably one of the type suitable for high temperature and ,pressure operations and which is not poisoned by sulfur.

Catalysts which may be used are heavy metals of the sixth group of the periodic system, especially molybdenum andv tungsten, but also chromium and uranium and compounds thereof', or tin, lead, vanadium, rhenium, manganese, zinc, cadmium, aluminum or cobalt or compounds thereof. Suitable strongly hydrogenating catalysts are for example the sulfldes of heavy metals, such as suliides of metals of the sixth group of the periodic system, `for example of molybdenum, tungsten or of nickel, cobalt, rhenium or a tungstate such as nickel tungstate. Catalysts having a less strongly hydrogenating action are, for example the oxides of the metals of groups 5 to 8, in

particular group 6 of the periodic system.

The invention will be further understood from the following description read in rconnection with the accompanying drawing which shows a diagrammaticl sketch of one type of apparatus for carrying out theprocess of the invention.

Referring 'to the drawing, .a hydrocarbon oil charging stock which may be crude residuum. gas oil, crude oil, heavy naphtha and the like, is charged through line I by means of pump 2 into a fractionating tower 3 which receives vapors from the conversion operation. In the fractionator 3 substantially all the vapors of higher boiling point than the desired motor fuel product are condensed and collected along with the unvaporized charging stock in the bottom of the fractionator which is withdrawn through the line 5. This material is forced by the pump 6 through the line 1 to a heating coil 8. In this heating coil the oil is subjected to conversion conditions which may be'temperatures of about '700-1200 F. and pressures of about 200-5000 pounds or more. Provision is made for adding normally gaseous hydrocarbons, ,such as butane, propane, a mixture of butane and propane, or mixed C4 cracked hydrocarbons, or a mixture of hydrocarbons of C1 to C4, such as natural gas or refinery gases, or cracking still gases. These gases may be added to the oil at the entrance of the coil through the valve controlled line I Il or at an intermediate point in the coil, such as at the point of incipient cracking, or at the point of incipient tar or fuel oil4 formation, through the line II. It is also provided that the hydrocarbons gases may be introduced through the line I2 into the heating coil I4 and heated to an elevated temperature and pressure, such as about 800-1'750 F. and pressures of 200-5000 pounds or more, then mixed with the hot products from the coil 8 in the line I5, leading to the reaction or soaking drum I8. In some cases it may be desirable to introduce the normally gaseous hydrocarbons through one or more or all of the lines In, II and I2. The products from the soaking drum I8 are transferred through the line I9 to a second soaking drum 20, wherein further reaction is allowed to take place.

Hydrogen is introduced through the line 22 and forced under high pressure, which may be substantially the same or slightly above that maintained in the reaction drums I8 and 20, by means of the pump 23 te heating coil 25. The use of this heating coil is optional and the coil 25 may be by-passed by suitable manipulation of valve 21 in the line 26 and valve 28 in the line 22. It is preferable to heat the hydrogen to sufficient temperature, say about 500-1200 F. whereby there will be no excessive reduction in temperature when the hydrogen is introduced into the reaction products from the coils 8 and I4. 'I'he hydrogen is conducted throughthe line 30 which is provided with manifolds 3I and 32 for introducing the hydrogen either into the products entering the -reaction drum I8 or the reaction drum 20. Reaction drums I8 and 20 may or may not be provided with a hydrogenation catalyst. It is preferable to provide at least the reaction drum 20 with a hydrogenation catalyst.

The reaction products from the drum 20 are transferred through the line 35 to a separator 36. This separator is preferablymaintained under high pressure and a low level of liquid products is maintained by continuously or intermit tently drawing off the fuel oil or tar from the bottom thereof through the valve controlled line 31. This tar draw-olf line ordinarily leads to a reduced pressure tar stripper in which the tar maybe flashed to produce a fuel oil bottoms and a distillate comprising gas oil and naphtha, a portion or all of which, preferably the gas oil at least, may be recycled to the system, for example to fractionator 3 or coil 8. Vapors evolved in the separator 86 are transferred through the vapor line 40 to the fractionator 3, referred to heretofore. Vapors including gasoline are removed from the top of the fractionator through the vapor line 42 and passed through a condenser 43 in which normally liquid hydrocarbons are condensed and passed through the run-down line 44 to accumulator 45, provided with a gas release line 41 and a liquid draw-off line 48. In the accumulator 45 a high pressure may be maintained and fixed gases, such as hydrogen, methane and ethane may be released through the line 41, if desired. The unstabilized motor fuel and gases are passed through the line 48 to a stabilizer 50 in which the motor fuel is stabilized by fractionating therefrom undesirable normally gaseous hydrocarbons. The resulting stabilized naphtha is withdrawn from the bottom of the stabilizer through the valve controlled line 5I. A portion or all of the xed gases, such as hydrogen, methane, ethane, may be released through the top of the stabilizerthrough the valve controlled line 52. A stabilizer side stream or reflux such as butane or propane or a mixture of butane and propane, or all or any desired portion of the normally gaseous hydrocarbons is withdrawn through the line 54 and forced by the pump 55 through the line 56 which communicates with lines I0, II and I2, referred to heretofore.

Extraneous gaseous hydrocarbons, such as natural gas, casinghead gasoline,'reflnery gases, etc., may be introduced through they line 60 and pump 6I into stabilizer 50.

-As an example of the operation of the process ofthe invention, a reduced crude was heated to incipient cracking, for example to a temperature of around 750 F., and normally gaseous hydrocarbons amounting to about 25% by volume, were then commingled therewith and the mixture subjected to further heating to a temperature of around 900 F. and the reaction productsl introduced into a soaking drum maintained under a temperature of around 890 F. and a pressure of about `300 pounds. The reaction products from the soaker were mixed with about 10% hydrogen and the mixture subjected to further reaction at a temperature of about 875 F. in another soaking drum. The reaction products were then introduced into a separator from which a fuel oil was withdrawn to a tar stripper.

A gas oil fraction was removed from the tar stripper and introduced as a reflux medium into a fractionator receiving vapors from the separator. The vapors comprising gasoline hydrocarbons were removed from the top of the fractionator, subjected to condensation and collected in a high pressure accumulator from which fixed gases were eliminated. The unstable condensate was introduced into a stabilizer in which a stable naphtha was withdrawn from the bottom and the remaining fixed gases were released from the top. About 10% of an extraneous product comprising mainly butane and propane was introduced into the stabilizer. A side stream, consisting principally of C3 and C4 hydrocarbons, was withdrawn from the stabilizer and recycled to the intermediate point of the heating coil, as

described heretofore.

An increased yield of about 7% of a stable, high grade motor fuel was obtained over that resulting from normal cracking of the hydrocarbon oil alone. Substantially less tar and fuel oil were produced. Also the tendency to coke formation in the reaction drums was substantially reduced.

While the process has been described in con- 'Ity nection with an operation involving clean circulation, it is to be understood that any well known or preferred type of cracking operation may be used in which suitable periods of reaction `may be obtained, either by soaking drums or soaking coils. One type of operation which is specifically contemplated is one involving a super-clean circulation in which two fractionating towers are used instead of the one shown in the drawing.

In such a type of operation a dirty recycle stock would be withdrawn from the bottom of the first tower and passed through a separate heatinvention, a crude residuum was heated to conmixture subjected to further reaction in the presence of the same catalyst. The final products of reaction were introduced into a separator in which a fuel oil was withdrawn, a major portion of which was recirculated to the reaction drums. The vapors were fractionated and the lrecycle stock recirculated to the heating coil.

The remaining vapors were condensed to separate the gasoline and the gases recirculated to the system. A high yield of antiknock motor fuel was obtained and substantial reduction in the yield of fuel oil was observed.

Obviously many modifications and .variations of the invention, as herelnbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed'as are indicated in'the appended claims.

I claim: l

1. A process for the conversion of higher boiling hydrocarbon oils into lower boiling hydro- -carbon oils which comprises raising the oil to temperatures of incipient cracking, then before substantial formation df coke forming materials adding normally gaseous hydrocarbons heavier than methane to the oil, further heating the mixture to cracking temperatures whereby coke formation is substantially retarded by said gaseous hydrocarbons, subjecting the mixture to reaction in the presence of a catalyst immune to sulfur poisoning to produce low boiling products from the oil and gaseous hydrocarbons and introducing hydrogen into the reaction zone to inhibit the formation of coke and tar and increase the yield of low boiling liquid products.

2. A process for the cracking of high boiling hydrocarbon oils to form gasoline boiling point hydrocarbons, which comprises heating thepil to cracking temperatures in a heating coil, introducing normally gaseous hydrocarbons heavier than methane into an intermediate point of said coil at about the temperature of incipient cracking to retard coke formation and to be converted into normally liquid hydrocarbons, subjecting the products from the cracking coil to reaction in the presence of alcatalyst immune to sulfur poisoning in a reaction zone and introducing hydrogen into the reaction zone whereby the formation of coke forming materials is substantially reduced and the yield of gasoline materially increased.

3. A process for the cracking of high boiling hydrocarbon oils to form gasoline boiling point hydrocarbons, which comprises heating the oil to incipient cracking temperatures and prior to substantial formation of coke forming materials,

commingling normally gaseous hydrocarbons heavier than methane withthe oil to retard coke formation, further heating the mixture to cracking temperatures, subjecting the mixture to reaction to produce low boiling oil products from the oils and gaseous hydrocarbons, then contacting I l hydrogen with the reaction products and subjecting the mixture to further reaction at conversion temperatures in the presence of a catalyst immune to sulfur poisoning to further prevent coke and increase the yield of gasoline.

` 4. A process for the cracking of high boiling hydrocarbon oils to form gasoline boiling point hydrocarbons, which comprises heating the oil to cracking temperatures and, prior to substantial formation of' coke forming materials, commin-` gling normally gaseous hydrocarbons heavier than methane with oil, subjecting the mixture to reaction in the presence of a catalyst immune to sulfur poisoning in a primary reaction Zone, commingling hydrogen with the reaction products and subjecting the mixture to further reaction in the presence of a catalyst immune to sulfur poisoning in a secondary reaction zone whereby coke formation is substantially retarded and said oil and gaseous hydrocarbons are converted into increased yields of low boiling products, including gasoline.

5. A process for the manufacture of gasoline, which comprises heating a high boiling hydrocarbon oil to cracking temperatures, commingling normally gaseous hydrocarbons between 2 and 5 carbon atoms with the hot oil prior to substantial formation of coke. forming materials whereby coke formation is substantially retarded, subjecting the mixture to conversion in a reaction zone to convert oils and gaseous hydrocarbons to gasoline in the presence of a catalyst immune to sulfur poisoning, introducing hydrogen into the reaction zone to further reduce coke formation and increase the yield of gasoline, separating from the reaction products a gasoline fraction and a normally gaseous hydrocarbon fraction containing hydrocarbons between 2 and 5 carbon atoms, and recycling said gaseous hydrocarbon for commingling with said hot oil.

v RUFUS L. SAVAGE, Jl. 

